Portal de Periódicos da CAPES

Preclinical Evaluation and Quantification of 18 F-FPEB as a Radioligand for PET Imaging of the Metabotropic Glutamate Receptor 5

2015; Society of Nuclear Medicine and Molecular Imaging; Volume: 56; Issue: 12 Linguagem: Inglês

10.2967/jnumed.115.162636

1535-5667

Bart de Laat, Gil Leurquin‐Sterk, Sofie Celen, Guy Bormans, Michel Koole, Koen Van Laere, Cindy Casteels,

Receptor Mechanisms and Signaling

The metabotropic glutamate receptor 5 (mGluR5) is a high-interest target for PET imaging because it plays a role in several pathologies, including addiction, schizophrenia, and fragile X syndrome. Methods: We studied the pharmacokinetics of 18 F-FPEB (3- 18 F-fluoro-5-(2-pyridinylethynyl)benzonitrile), a selective PET radioligand for mGluR5, and used it to quantify mGluR5 in rat brain. Quantification was performed using both arterial sampling in combination with compartment models and simplified reference methods. The simplified reference tissue model (SRTM), Ichise9s original multi-linear reference tissue model (MRTM O ), and Logan noninvasive were tested as reference models with nondisplaceable binding (BP ND ) as outcome parameter. Additionally, test–retest scans were obtained in 6 animals. Results: 18 F-FPEB uptake in rat brain was consistent with its known distribution. No radiometabolites were present in the brain, and binding was specific as shown in blocking experiments, which also confirmed the cerebellum as a viable reference region. A 2-tissue-compartment model was used to determine BP ND for the striatum (11.7 ± 1.5), nucleus accumbens (10.6 ± 2.0), hippocampus (9.0 ± 1.2), cortex (7.2 ± 1.0), and thalamus (4.0 ± 0.9). Reference methods were able to estimate these values with small bias (<2%). Test–retest analysis showed high repeatability between scans below 6%, also for shorter scan durations of 30 and 60 min. Conclusion: Because of its favorable reversible kinetics, high specificity, and absence of brain radiometabolites 18 F-FPEB proves a highly useful tracer for in vivo visualization of the mGluR5 in rat brain. Moreover, reference tissue models allow noninvasive, rapid scanning with good test–retest.